1. Field of the Invention
The present invention relates to a device and method for resolving or removing atherosclerotic plaque buildup or tissue in a blood vessel in order to restore necessary blood flow. The device includes a hollow catheter with a hollow tip member having an electrode for actively eroding, by means of high frequency high voltage electric current, atherosclerotic plaque areas or unwanted tissue within a blood vessel. The current generated at the electrode through the fatty material resolves the fatty material of the plaque and the residue of same may be removed through the hollow catheter.
2. Description of the Prior Art
Heretofore, various body insertable devices, such as catheters, having means for delivering impulses of electric current have been proposed for delivering electric current to internal organs, cavities or orifices of a body.
Such devices have generally been used with one electrode external of the body, and with means for delivery of irrigant fluid to or from the body.
Examples of some of the previously proposed devices are disclosed in the following patents:
______________________________________ U.S. PAT. NO. PATENTEE ______________________________________ Re. 27,569 Ackerman 452,220 Gunning 552,832 Fort 623,022 Johnson 4,060,086 Storz 4,429,694 McGreevy ______________________________________
The McGreevy U.S. Pat. No. 4,429,694 discloses an electrosurgical generator for generating waveforms for electrosurgical fulguration.
The Ackerman U.S. Pat. No. Re. 27,569 discloses a catheter which is designed for insertion through the chest and into the heart specifically for the purpose of introduction of electrical stimulation during cardiac arrest. When the heart has ceased to beat, a generated impulse is provided which is capable of delivering electric current approximating in strength, frequency and distribution the normal current of the heart. No reference is made to a hollow catheter or to a tip thereof which can be supplied with sufficient power for removal of plaque or tissue from a blood vessel.
The Gunning U.S. Pat. No. 452,220 discloses a surgical electrode device in the form of a solid catheter composed of electrically discrete coaxially movable electrodes. The electrodes of Gunning are connected to a battery so that direct current may be introduced to an organ or part of the body after the device is inserted through a body orifice. The Gunning catheter is not hollow, does not use high frequency current and is used in a different manner and for a different purpose than the device of the present invention.
The Fort U.S. Pat. No. 552,832 discloses a catheter for treatment of strictures in body orifices, e.g. urethra, esophagus, uterus or rectum. The catheter includes one electrode in the middle of the catheter which is defined by a bowed platinum plate or wire which projects to one side of the catheter. Another electrode is applied externally to the body, for example, on the abdomen whereby current is passed through the stricture and acts "electrolytically or electrochemically thereupon". Fort does not teach a hollow electrode tip catheter which can be used for eroding tissue in vessels.
The Johnson U.S. Pat. No. 623,022 discloses a catheter which is adapted for insertion into a body cavity and which is allegedly capable of delivering an electric current to the body. The electric current was believed to have some curative powers and no reference is made in this patent to erosion of plaque or tissue in a vessel. The catheter can be used for delivering fluid into the body and the electric current allegedly flows from the catheter through the fluid into the body.
No metallic surface comes into contact with the mucous surface, and hence, the current is not concentrated at any point of contact, but is diffused by the liquid so that comparatively heavy current may be used without harm to the body parts. There is no teaching of high frequency current, bipolarity, or electro-surgery in the Johnson patent and this catheter is clearly used in an electrochemical manner and not for electrical erosion of plaque or tissue.
The Storz U.S. Pat. No. 4,060,086 discloses an endoscope which is an instrument for visually examining the inside of a hollow organ. This particular endoscope includes a loop-like electrode and has a body which is inflexible and which is not designed for use in cleaning blood vessels but which is arranged for transurethral operations. Cutting action is carried on by an inner cutting edge of the endoscope in combination with an electrically charged loop of wire which sparks. The exact mechanism and its operation are unclear. A washing agent is supplied and discharged through the endoscope.
As will be described in greater detail hereinafter, the device and method of the present invention for resolving atherosclerotic plaques and unwanted tissue differ from the devices and methods previously proposed by providing a catheter which is sized to be received in a blood vessel and which has an erosion electrode localized near a hollow tip member mounted at the distal end of the catheter. The catheter is flexible and therefore manipulatable into and through the lumen of a blood vessel and can be positioned therein proximate atherosclerotic plaque or unwanted tissue in the blood vessel. High frequency high voltage electric current is generated and supplied to the atherosclerotic plaques or tissue for a predetermined period of time to resolve the plaque or tissue. In particular, the erosion resulting from high frequency high voltage current about the electrode positioned proximate the tip of the device member actively resolves plaque or erodes tissue.
In one preferred embodiment of the device of the present invention, there is provided a tubular hollow tip member open at the distal end thereof and communicating with a flexible and elongated hollow catheter body. The eroded debris resulting from the intermittent application of high frequency high voltage current about the electrode is conveniently carried out of the catheter by a trident connection at the proximal end. In between applications of the current, a low voltage direct current is passed through the plaque or tissue for making an impedance measurement to determine if a sufficient amount of plaque has been resolved or tissue eroded.
The electrosurgical device of the present invention employs the application of electric current directly to an area of plaque or tissue buildup for resolving, ablating or removing the buildup and differs from copending U.S. application Ser. No. 536,852 filed Sep. 28, 1983 by Harold Herschenson for: PLAQUE RESOLVING DEVICE AND METHOD, which resolves plaque by heating plaque with a heat conductive member at the tip of a catheter heated by an electric coil.